Electrolyte Supplementation

Electrolytes supplements are commonly given to many horses, particularly in the summer months. When the temperature rises, the amount of sweat the horse produces increases. Additionally, in Ontario, our horses are often ridden more frequently in the warmer weather.

What are electrolytes?

Electrolytes are a class of minerals that dissociate into electrically charged ions in water. They play a key role in the maintenance of fluid balance, osmotic pressure and are imperative to healthy nerve and muscle activity. For horses, sweating is the primary method of thermoregulation during exercise. Therefore, when a horse is working, especially in a hotter climate, their electrolyte losses can be substantial.

Horse sweat is considered hypertonic, or isotonic, meaning that the concentration of electrolytes in the sweat is higher than the concentration of electrolytes in the blood. This differs from humans, as the sweat that humans produce is hypotonic. There is visual evidence of this when a horse sweats, as you will often be able to see the presence of salt on their coat. If we compare sweat losses in horses and humans, adjusted for surface area, the horse will sweat up to three times the amount of sweat as humans!

The main electrolytes lost in equine sweat are sodium (Na+), chloride (Cl), and potassium (K+). Magnesium (Mg2+) and calcium (Cl2+) are also lost; however, they are lost in smaller quantities. The need for electrolyte supplementation will depend on factors such as the duration and intensity of exercise, the heat and humidity they horse is working in, and if they are acclimatized to that environment or not.

For horses that are at maintenance, their electrolyte requirements will generally be met with a forage-based balanced diet and supplemental salt. However, when horses are in regular training, competition, or prolonged transport, it may warrant additional electrolyte supplementation. If you are unsure if your horse requires additional electrolytes, you can always consult your veterinarian or nutritionist.

Why should they be supplemented?

When a horse is exercising and sweating, the sodium levels in their blood are normally lower than the pre-exercise levels. This can reduce their desire to drink water after exercise. Therefore, when a horse is given electrolytes after working it will increase the concentration of sodium in the blood and in turn, stimulate them to drink.

Additionally, due to the high concentrations of electrolytes lost in sweat, their requirements increase when exercising. When choosing an electrolyte supplement for your horse it is important to use a product that mimics what the horse loses in their sweat and provide them with free choice access to fresh water.

What to look for in an electrolyte supplement?

For my clients, I recommend being cautious of the commercial electrolytes that provide large amounts of sugar (often dextrose). Of course, it is unnecessary for sugar to be added to an electrolyte supplement as this is not something that is lost through the sweat. However, sugar is a popular addition to electrolytes as it increases the palatability of the product. If your horse is finicky, opting for a product that does contain dextrose is preferable as the product only does its job if they consume it!

There were some prior claims that sugar increased the uptake of electrolytes, but equine research has not supported this claim. A 2013 study (Pagan et al. 2013) used thoroughbred horses and illustrated that an addition of dextrose to the electrolyte supplement did not increase the rate of absorption or the retention of electrolytes.

The inclusion of a minimal amount of sugar can be valuable for palatability, however, when there are large amounts of sugar, the concentration of electrolytes is lower which in turn may result in a less effective product.

Therefore, when looking for a supplement for your horse, it is recommended to choose a product that primarily supplies sodium, chloride, and potassium as those are the electrolytes lost in the highest concentrations, with lesser concentrations of magnesium and calcium.

Encouraging Hydration

We have all heard the saying “you can lead a horse to water, but can’t make them drink”, however, we can encourage it!

The gold standard for electrolyte supplementation is to train your horse to drink a water/electrolyte mixture 1-hour before exercise or transport. This is not always feasible, therefore, providing the electrolyte/water mixture afterwards to replenish losses is also an option.

A word of caution with electrolyte supplementation is that you must always ensure adequate water access. When you mix an electrolyte supplement with water, it is recommended to always provide your horse with both the mixture as well as a bucket of plain fresh water. If your horse does not prefer the taste of the water mixture, it is crucial that they are not being discouraged of drinking.

Additionally, if you are mixing the electrolyte product with water it is recommended to train your horse to drink it at home first, prior to using it at competition. Introducing something new, such as an electrolyte supplement mixed with their water, in a more stressful environment will not set you up for success. Familiarizing your horse with the product and mixture prior to situations in which you need them to consume it is preferable. That way, you can ensure you are purchasing a product that they like, and are used to, prior to offering it for the first time before a competition or transport event. Think of it like how you practice loading your horse on the trailer, prior to the morning of the show!

Take Home Message

Overall, if your horse is not in work, simply providing them with a balanced forage-based diet, and supplemental salt is adequate. However, for horses in regular training, competition, undergoing transportation, or even just sweating due to hot weather, you can add an electrolyte that matches the losses in sweat. The electrolyte will ideally be mixed with water and provided to the horse, however, adding it to their feed is also an option, you just want to ensure they are not seriously dehydrated when this is done.

To conclude, this article simply scratches the surface of what ingredients to look for in an electrolyte supplement as well as guidance on how to provide them to your horse. If you have any specific questions about how to optimally provide your horse with electrolytes, it is recommended to consult your nutritionist or veterinarian.

By: Madeline Boast, MSc. Equine Nutrition


Waller, A. P., & Lindinger, M. I. (2021). Pre‐loading large volume oral electrolytes: tracing fluid and ion fluxes in horses during rest, exercise, and recovery. The Journal of Physiology599(16), 3879-3896.

Pagan, J.D., B.M. Waldridge, J. Lange. 2013. Dextrose does not affect rate of absorption or retention of electrolytes in idle Thoroughbreds. Journal of Equine Veterinary Science. 33(5):349-350. (Proceedings of the 2013 Equine Science Society Symposium)

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